It is known to use semiconductor devices that are made for example of gallium nitride or silicon carbide for detecting a chemical substance contained in a fluid. Corresponding semiconductor devices may be formed as chemically sensitive field-effect transistors.
The focus of developments so far with respect to such chemically sensitive semiconductor devices has been in particular on their optimum design for detecting a specific chemical substance. In the case of such detection, typically a drift of the offset (known as “baseline drift”) is observed. Such an offset drift has various underlying causes with different time constants. These include in particular the generation, charging and discharging of interface states, the redistribution of free charge carriers from trapping sites, the removal of free charge carriers from trapping sites, the generation of defects, the presence of mobile charges in the dielectrics and the changes in the semiconductor, which for weak electrical loads are comparatively small. Altogether, an offset drift has the effect that spontaneously occurring, gas-induced detection signals may only be detectable by observing changes of detection signals, but quantitative measurements are not possible. There are no absolutely measuring gas sensors on the basis of the principle of chemically sensitive field-effect transistors.